Question

(8х+91)/7=21   

Answer 1

(8х+91)/7=21 |•7
8х+91=147
8х=147-91
8х=56
х=56/8
х=7

Answer 2

ох спасибо большое

Answer 3

$(8x+91)/7=21$
$8x+91=21*7$
$8x=147-91$
$8x=56$
$x=56:8$
$x=7$